Abstract: The effect of shot peening and roller burnishing on the fatigue performance of the γ(TiAl)
alloy Ti-45Al-9Nb-0.2C was investigated over a wide range of processing intensities. At optimized
conditions shot peening and roller burnishing can markedly improve the fatigue strength at ambient
temperatures. For temperatures above 650 °C, the residual compressive stresses induced by shot
peening and roller burnishing quickly relax. This indicates that, at elevated temperatures, surface
roughness and dislocation strengthening become more important for the fatigue performance of
mechanically surface-treated components. Roller burnishing leads to much lower surface roughness
than shot peening, resulting in more effective improvement of high temperature fatigue performance.
However, surface strengthening by shot peening can also be beneficial for the fatigue performance at
elevated temperatures, when the surface roughness is reduced by subsequent polishing.

Abstract: The efficiency of aircraft and industrial gas turbines and combustion engines depends on
the maximum operation temperature and, therefore, on the properties of the commercial high
temperature materials. In the temperature range 500°C to 750°C γ-titanium aluminides especially
alloys of the third generation represent an attractive alternative to the established nickel-base
superalloys which have the double density. Due to superimposed cyclic thermal and cyclic
mechanical loadings during start-up and shut-down operations structural components in gas turbines
and combustion engines may not only be exposed to isothermal but also to thermo-mechanical fatigue
(TMF). In this study the cyclic deformation and fatigue behaviour under thermo-mechanical load of
the γ-TiAl alloy TNB-V5 with near-gamma microstructure is evaluated. To set a fatigue-life relation
strain-controlled thermo-mechanical fatigue tests were carried out with two different strain ranges,
different temperature-strain cycles and different temperature ranges from 400°C to 800°C. Additional
low-cycle fatigue (LCF) tests were performed at 400°C, 600°C and 800°C for comparison. Cyclic
deformation curves, stress-strain hysteresis loops and fatigue lives of the tests are presented. The
shortest fatigue lives are always observed in out-of phase (OP) tests, the longest in in-phase (IP) tests.
Clockwise-diamond (CD) and counter-clockwise diamond (CCD) testing yield similar fatigue lives
intermediate between those of OP and IP tests. For a general life prediction the double-logarithmic
plot of the damage parameter by Smith, Watson and Topper vs. fatigue life is well suitable.

Abstract: The microstructure of ternary Al3(Sc1-yREy) intermetallic compounds (where RE is one of
the rare-earth elements La, Ce, Nd, Sm, Eu, Yb or Lu), was investigated as a function of RE
concentration for 0

Abstract: Isothermal low cycle fatigue (LCF) behaviours of a third generation titanium
aluminide based γ-TiAl alloy with duplex microstructure were investigated under the various
test conditions, including temperature (550°C-750°C), total strain amplitude (0.3%-0.6%) and
environment (air and vacuum), in order to clarify the fatigue life, deformation characters and
fracture process of the alloy during LCF. The plastic strain accumulation has a great
contribution to LCF damage. With increasing total strain range, LCF life decreases distinctly.
Under the small total strain amplitude (≤0.4%), the increase of test temperature enforces
microstructure resistance to LCF fracture. However, the increase of test temperature together
with large total strain amplitude (>0.5%) accelerates the microstructural degradation, which
behaves the dissolution of α2 lamellae and recrystallization of γ phase, resulting in great LCF
damage. Moreover, environment brittlement during high temperature exposure to air
influences the initiation process of fatigue cracks. The fracture mechanisms at various test
conditions were analyzed.

Abstract: In order to investigate the intergranular and pitting corrosion behavior of Fe-25Al-6Cr
intermetallic compounds containing Mo, Nb and B, 11 kinds of Fe-25Al were prepared by arc
melting in Ar gas, using high purity aluminum and iron. The fabricated materials were heat treated
for homogenious structure and stabilization of the iron aluminides. The electrochemical methods
were used for interganular and pitting corrosion. Effects of Mo, Cr, Nb and B on the repassivation
current density(Ir) and the active current density(Ia) of Fe-25Al-6Cr were recorded in the following
order: MoCr>Nb>B, from the highest to the lowest respectively.

Abstract: Microstructures and mechanical properties of Ni3Al based intermetallic alloys produced
by vacuum arc melting and vacuum induction melting were investigated in terms of phase analysis
using scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy
(EDS), X-ray diffractometer and tensile test machine. The duplex microstructural feature consisting
of γ’ matrix phase and small intermetallic dispersoids was observed to be distributed over the whole
microstructure in the Zr and/or Mo-added samples. From the SEM-EDS analysis of the alloys, it is
clearly confirmed that the Mo is solved both into γ’ matrix phase and intermetallic phase while Zr has
a role to form an intermetallic Ni5Zr phase for the entire alloys investigated. The ultimate tensile
strength of the present alloy was superior to iron-based and Ni-based die materials especially in the
high temperature region. The mechanical results obtained will be discussed in correlation with
microstructural observations, phase analyses.

Abstract: The mechanism of grain boundary embrittlement and the improvement of the tensile
ductility afforded by alloy addition or heat treatment was investigated in an Fe-Mn-Ni alloy. The
precipitation of θ-MnNi intermetallic particles was observed at the prior austenite or interlath
boundaries during the aging treatment and this was believed to be responsible for the grain
boundary embrittlement of these alloys. After prolonged aging or aging at higher temperatures
above 520°C, these metastable intermetallic particles were transformed into the thermodynamically
stable austenite phase, thereby leading to the recovery of the grain boundary strength. The addition
of Mo caused the grain boundary precipitate to be changed to austenite and resulted in a significant
improvement in the tensile ductility after aging.

Abstract: This study was carried out to newly develop the fluxes and filler metals for brazing
magnesium alloy AZ31B more easily at lower temperatures. Furthermore, surface preparation was
developed to improve the brazeability of magnesium alloy. The main results obtained are as follows.
We could successfully develop the fluxes that consisted of chlorides containing Ca ion and Li ion,
which made the faying surface of the magnesium alloy active at around 450°C. In addition, we
succeeded in developing the filler metals with the melting temperatures lower than 490°C which
were Mg-Sn-In system containing a small amount of Al to lower the melting temperature. Surface
preparation for magnesium alloy by immersion in aqueous solution containing halogen ion
improved remarkably the brazeability of the magnesium alloy. Using the surface preparation
together, the fluxes and filler metals could achieve the brazed joints with a high strength equivalent
to that of the base metal.